Döbereiner's triads
Johann Wolfgang Döbereiner, who attempted to sort the elements in an order which consisted of triads.
In the history of the periodic table, Döbereiner's triads were an early attempt to sort the elements into some logical order by their physical properties. In 1829, the German chemist Johann Wolfgang Döbereiner published[1] a report of his previous observations that there were groups of three elements (hence "triads") which had similar physical properties. He also noted that some quantifiable properties of elements (e.g. atomic weight and density) in a triad followed a trend whereby the value of the middle element in the triad would be exactly or near exactly predicted by taking the arithmetic mean of values for that property of the other two elements.
| Element 1 Atomic mass |
Element 2 Actual atomic mass Mean of 1 & 3 |
Element 3 Atomic mass |
|---|---|---|
| Lithium 6.9 |
Sodium 23.0 23.0 |
Potassium 39.1 |
| Calcium 40.1 |
Strontium 87.6 88.7 |
Barium 137.3 |
| Chlorine 35.5 |
Bromine 79.9 81.2 |
Iodine 126.9 |
| Sulfur 32.1 |
Selenium 79.0 79.9 |
Tellurium 127.6 |
| Carbon 12.0 |
Nitrogen 14.0 14.0 |
Oxygen 16.0 |
| Iron 55.8 |
Cobalt 58.9 57.3 |
Nickel 58.7 |
References
- ↑ Döbereiner, Johann Wolfgang (1829). "An Attempt to Group Elementary Substances according to Their Analogies". Annalen der Physik und Chemie. 15: 301–307.
an attempt which I made twelve years ago to group substances by their analogies.
- "Johann Wolfgang Dobereiner". Archived from the original on 2016-03-23. Retrieved 2016-03-23.
- "A Historic Overview: Mendeleev and the Periodic Table" (PDF). Retrieved 2013-01-15.
This article is issued from Wikipedia - version of the 11/28/2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.